Investment Securities (Restrictions on Redemption Frequency and Advance Notice Requirements) (Details) (Hedge funds, USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Investment securities
Other long-term investments	$ 117.2
Distributions from inactive hedge funds	2.5
Redemption requests	2.1
30-59 days notice
Investment securities
Other long-term investments	30.1
60-89 days notice
Investment securities
Other long-term investments	52.4
90-119 days notice
Investment securities
Other long-term investments	19.5
120+ days notice
Investment securities
Other long-term investments	15.2
Monthly
Investment securities
Other long-term investments	5.6
Monthly | 30-59 days notice
Investment securities
Other long-term investments	0
Monthly | 60-89 days notice
Investment securities
Other long-term investments	0
Monthly | 90-119 days notice
Investment securities
Other long-term investments	0
Monthly | 120+ days notice
Investment securities
Other long-term investments	5.6
Quarterly
Investment securities
Other long-term investments	77.9
Quarterly | 30-59 days notice
Investment securities
Other long-term investments	28.5
Quarterly | 60-89 days notice
Investment securities
Other long-term investments	29.2
Quarterly | 90-119 days notice
Investment securities
Other long-term investments	10.8
Quarterly | 120+ days notice
Investment securities
Other long-term investments	9.4
Semi-annual
Investment securities
Other long-term investments	23.2
Semi-annual | 30-59 days notice
Investment securities
Other long-term investments	0
Semi-annual | 60-89 days notice
Investment securities
Other long-term investments	23.2
Semi-annual | 90-119 days notice
Investment securities
Other long-term investments	0
Semi-annual | 120+ days notice
Investment securities
Other long-term investments	0
Annual
Investment securities
Other long-term investments	10.5
Annual | 30-59 days notice
Investment securities
Other long-term investments	1.6
Annual | 60-89 days notice
Investment securities
Other long-term investments	0
Annual | 90-119 days notice
Investment securities
Other long-term investments	8.7
Annual | 120+ days notice
Investment securities
Other long-term investments	$ 0.2